JP2872285B2 - Image processing apparatus and image processing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image processing apparatus and an image processing method.

[Conventional technology]

Conventionally, a color image processing apparatus determines an input signal and automatically determines whether a document is a black and white document or a color document, and executes a monochrome black copy for a black and white document and a color copy for a color document. Are known.

Another technology is to detect black characters in a document, print the black characters in a single black color, and print the rest in color, so that the black characters in a color document can be copied clearly without color shift. Proposed by the applicant.

[Problems to be solved by the invention]

However, based on the above-mentioned technology, the type of document (black and white or color) is determined, and the copy mode is selected.
There has been no apparatus having a high image processing capability of extracting a black character portion in a document and outputting without color misregistration.

However, in the case where the above-described auto color determination and a unique determination circuit for black monochrome printing are separately provided, there is a problem that the device configuration becomes complicated. On the other hand, due to variations in various characteristics of the reading optical system, different judgment results may occur even for the same original.

Further, in the copy output of the same document, whether to determine chromatic or achromatic may differ depending on the purpose of use, preference, etc. of the operator.

Also, in a color image, the reproducibility of a black character portion may be reduced due to color misregistration, and it is necessary to perform a dedicated process different from other regions in the color image for the black character portion. There is no need to perform dedicated processing on the image.

The present invention has been made in view of the above circumstances, and has as its object to provide an image processing apparatus and an image processing method that provide high-precision black-and-white / color determination and black character determination and that can efficiently improve image reproducibility. .

[Means for Solving the Problems] The invention according to claim 1 of the present invention is a means for determining black and white / color of an input image based on an input image signal (in this embodiment,
Means for determining a black character on the basis of the input image signal (same as those in FIGS. 108, 109, and 14; EDGE to BL1 in FIGS. Means for switching between the monochrome / color determination and the black character determination conditions (same as above, CPU 118 and page 44, lines 10 to 13)
(Corresponding to a row).

The invention according to claim 2 is dependent on claim 1, wherein the monochrome / color determination and the black character determination use the same saturation determination method, and the monochrome / color determination emphasizes chromatic color determination. (In this embodiment, the point of using the table determination shown in FIG.
Line).

According to a third aspect of the present invention, it is determined whether the original is monochrome or color at the time of preliminary scanning of the original (in the present embodiment, the tenth embodiment).
If the original is color according to the determination result, black character processing is performed when the original is copied at the time of main scanning (in the present embodiment, the 14th processing is performed in FIGS.
(Corresponding to performing the process of FIG. 1A).

A fourth aspect is dependent on the third aspect, wherein at least a saturation determination is made in a document determination for determining whether the document image is monochrome or color and a black character portion determination in the black character processing. (In this embodiment,
(Corresponding to FIG. 2 109).

5. An input means for inputting image data corresponding to a document (corresponding to 210 in FIG. 2 in the present embodiment), and from the image data input by the input means, whether the document is a color document or a monochrome document. 10 (line 17 to line 20, page 22, and FIG. 10).
9, an identification means for identifying a black character portion of the original for each pixel from the edge information of the image data input by the input means (same as in FIGS. 108, 109, and 14). Processing means for performing black character processing on the identified black character portion if the color document is determined by the determination means (equivalent to determining that EDGE to BL1 is 1) (determination at 904 in FIG. 11). 906 to 909
(Corresponding to performing the 14th (a) process).

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[First Embodiment] FIG. 2 shows an overall configuration diagram of a digital color copying machine to which the present invention is applied in this embodiment.

In FIG. 2, reference numeral 201 denotes a portion for reading a document by an image scanner and performing digital signal processing. Also 20
Reference numeral 2 denotes a printer unit which prints out an image corresponding to the original image read by the image scanner unit 201 on a sheet in full color.

In the image scanner unit 201, reference numeral 200 denotes a mirror pressure plate, and a document 204 on a platen glass (hereinafter, platen) 203 is
Irradiated by platen 205, guided to mirrors 206, 207, 208,
An image is formed on a three-line sensor (hereinafter referred to as CCD) 210 by a lens 209 and sent to a signal processing unit 211 as full-color information red (R), green (G), and blue (B) components. Here, the three-line sensor 210 is configured such that R, G, and B line sensors are arranged in parallel at a spatial distance, and generate a plurality of color component signals based on different spectral characteristics.

Note that 205 and 206 are speeds v, and 207 and 208 are 1/2 v mechanically move in the direction perpendicular to the electrical scanning direction of the line sensor to scan the entire original. The signal processing unit 211 electrically processes the read signal, decomposes the signals into magenta (M), cyan (C), yellow (Y), and black (Bk) components, and sends them to the printer unit 202. In addition, one component of M, C, Y, and Bk is sent to the printer unit 202 for one document scan in the image scanner unit 201, and one printer out is completed by a total of four document scans.

M, C, Y or sent from the image scanner 201
The Bk image signal is sent to the laser driver 212. The laser driver 212 modulates and drives the semiconductor laser 213 according to the image signal. The laser beam scans on the photosensitive drum 217 via the polygon mirror 214, the f-θ lens 215, and the mirror 216.

Reference numeral 218 denotes a rotary developing unit, which includes a magenta developing unit 219, a cyan developing unit 200, a yellow developing unit 221, and a black developing unit 222. The four developing units alternately contact the photosensitive drum 217 and are formed on the photosensitive drum 217. The developed electrostatic latent image is developed with toner.

Reference numeral 223 denotes a transfer drum which winds a sheet fed from the sheet cassette 224 or 225 around the transfer drum 223 and transfers an image developed on the photosensitive drum 217 to the sheet.

After the four colors M, C, Y, and Bk are sequentially transferred in this manner,
The sheet passes through the fixing unit 226 and is discharged.

FIG. 3 is an internal block diagram of the image scanner unit 201. In FIG. 3, reference numeral 101 denotes a counter.
The main scanning address 102 for designating the main scanning position of is output. That is, when the horizontal synchronization signal HSYNC is 1, it is set to a predetermined value by a CPU (not shown) and incremented by the clock signal CLK of the pixel.

The image formed on the CCD 210 has three line sensors 30
The photoelectric conversion is performed at 1,302,303, and the R component, G
Component, B component as a read signal, amplifiers 304, 305, 306,
Sample hold circuits 307, 308, 309 and A / D converters 310, 31
Digital image signal 313 of 8 bits for each color through 1,312
(R), 314 (G), and 315 (B) are output to the signal processing unit 211.

[Flow of Signal] FIG. 1 is a diagram showing the flow of a signal in the present embodiment centering on the signal processing unit 211.

Here, reference numeral 211 denotes a signal processing unit shown in FIG. 2, reference numeral 201 denotes a printer unit, and reference numeral 250 denotes a control unit mainly including a CPU.

In the figure, CLK is a clock signal for transferring pixels, and HSYNC
Is a horizontal synchronizing signal, which is a synchronizing signal for starting main scanning, and CLK4 is a clock signal for generating a 400-line screen described later, as shown in FIG.

Further, VSYNC is a signal indicating a sub-scanning image output section.

Reference numerals 101 and 102 denote delay memories for adjusting the spatial displacement of the three line sensors 301, 302, and 303. Each 101 generates a delay of 36 lines and 102 generates a delay of 18 lines. The delay memory is, for example, a FIFO (First In First O
ut) It can be composed of memory.

Reference numerals 103, 104, and 105 denote -LOG conversion circuits, which perform luminance density conversion and complementary color conversion.

That is, for R, G, B, A C (cyan) M and a (magenta) Y (yellow) signal are generated by the following relational expression.

 Reference numeral 106 denotes a black component extraction circuit, which generates a black component Bk signal by the following equation: Bk = min (Y, M, C).

107 is a UCR (under color removal) and masking circuit which removes an under color (black) component, furthermore, a CCD spectral sensitivity characteristic and
This portion corrects the difference in the spectral sensitivity characteristics of the toner in the printer section, and generates a signal of Y ', M', C ', or Bk', which is a signal for actually developing the toner.

On the other hand, a character edge extraction unit 108 detects the edge continuity of the G (green) component signal, detects the character edge, and generates an EDGE1 signal. A color determination unit 109 generates a BL1 signal indicating that the read signal is black and a COL1 signal indicating that the read signal is chromatic based on the three primary color signals of R, G, and B.

Reference numeral 110 denotes a control signal generation unit which sends control signals to various circuits described later based on the determination results of the character edge extraction unit 108 and the color determination unit 109.

Reference numeral 112 denotes a mixing circuit of a color signal and a monochrome black signal,
The output X ₁ (Y ′, M ′, C ′ or B ′) of the masking circuit 107
k ′) and X ₂ (M) before masking, weight α = G
AIN1, β = GAIN2 multiplied Y = α × X ₁ + β × X ₂ (α, β =
0-1).

An output signal from the mixing circuit 112 is filtered by a spatial filter 113, density-corrected by a density correction circuit 114, and a laser is driven by a PWM (pulse width modulation circuit) 115 to obtain an image output 116.

In the 250 control units, 118 is a CPU, which controls the entire apparatus.

Reference numeral 120 denotes a ROM and a RAM, which store a control program and data. Reference numeral 117 denotes a chromatic color pixel count circuit, which counts the number of chromatic color pixels in the document.

FIG. 4 is a block diagram of the saturation judgment of the color judgment unit 109.

In FIG. 4, reference numeral 1301 denotes a MAX / MIN detector;
Reference numerals 1309 to 1309 denote selectors, and reference numerals 1310 to 1315 denote subtracters, which output AB for inputs A and B. 1316 to 1323 are comparators for inputs A and B, 1316, 1319 are 2A> B, 1317, 1320, 1322, 1323 are A> B, 1318, 1321 are 1 if A> 2B. Output, otherwise output 0. 1324-1328 is an AND gate, 1329 is a NOR gate, 11
30 is a NAND gate.

In the above configuration, the MAX / MIN detector 1301 has the fifth-
The circuit shown in FIG. 1 is used. In FIG. 5-1, 1350,1
351,1352 are comparators, R> G, G> B, B respectively
If> R, 1 is output. The circuit shown in FIG.
As shown in FIG. 5-2, the following judgment signals S00, S01, S02, S1
0, S11 and S12 are generated. That is, when MAX is R or when R, G, and B are all equal, S00
= 1, S01 = S02 = 0, if MAX is G, S01 = 1, S00 = S02 = 0, if MAX is B, S02 = 1, S00 = S01 = 0, MIN is R, or If R, G, B are all equal,
When S10 = 1, S11 = S12 = 0, MIN is G, S11 = 1, S10 = S12 = 0, and when MIN is B, S12 = 1, S10 = S11 = 0.

For example, when MAX is R, the comparator 1350 outputs 1 because R> G and R ≧ B, and the comparator 1352 outputs “1”.
Outputs 0. AND1 outputs 1 and OR1 outputs 1. AND2 and AND3 output 0. That is, S00 = 1,
S01 = S02 = 0. The result of performing the same determination is the fifth-
2 is a table shown in FIG.

Outputs S00, S01, S02 of the MAX / MIN detector are input to a selector 1302, and outputs S10, S11, S12 are input to selectors 1303-1309.

The selectors 1302-1309 are composed of an AND circuit and an OR circuit as shown in FIG. According to this selector, the sixth
As shown in FIG. 2, A is output when S0 = 1, S1 = S2 = 0 for inputs A, B, and C, and B is output when S1 = 1, S0 = S2 = 0, and S2 C is output when = 1, S0 = S1 = 0. In this embodiment, R, G, B signals correspond to inputs A, B, C.

In this embodiment, the pixel color determination is performed by setting the maximum value of the R, G, and B signals to MAX and the minimum value to MIN, and determining the values of A, B, C, and D as shown in FIG. This is performed by dividing into four regions.

In other words, in the achromatic region, the difference between MAX and MIN is small, and the closer to chromatic color, the larger the difference between MAX and MIN. The MAX-MIN plane is divided by.

Specifically, ka, kb, kc, ia, ib, ic, WMX, and WMN are assumed to be predetermined constants, and are divided into four areas A, B, C, and D as shown in FIG. 7-1. .

A is a dark achromatic (black) area. (MAX, MIN)
Is included in this area if MIN ≦ WMN or MAX ≦ WMX, and Is to meet all of

B is a region between the dark achromatic color and the chromatic color. (MAX,
MIN) is included in this area if MIN ≦ WMN or MAX ≦ WMX, and Satisfy one of Is to meet all of

C is a chromatic color area. The condition that (MAX, MIN) is included in this area is that MIN ≦ WMN or MAX ≦ WMX, and To satisfy any of the following.

D is a bright achromatic (white) area. (MAX, MI
N) is included in this area Is to satisfy both.

FIG. 7-2 shows output signals for the respective states A, B, C and D. That is, BL1 = 1, UNK1 = COL1 = 0 when included in area A, UNK = 1, BL1 = COL1 = 0 when included in area B, and COL1 = 1, when included in area C BL1 = UNK1 = 0, and when included in the D area, BL1 = UNK1 = COL1 = 0.

The above-mentioned area determination is performed by the circuits 1304 to 1330 in FIG. Selector 1302, depending on the output of MAX / MIN detector 1301,
1303 selects the MAX signal and the MIN signal from among R, G and B, respectively, and the selectors 1304-1309 also select the values of the constants ka, kb, kc, ia, ib and ic in conjunction with the selector 1303. . For example, when MAX is an R signal and MIN is a G signal, the selector 1304
KAG, 1305 is KBG, 1306 is KCG, 1307 is iAG, 1308 is iBG, 1
Reference numeral 309 selects iCG, which are constants ka, kb, kc, ia, ib, and ic, respectively. The reason why the values of the constants ka, kb, kc, ia, ib, and ic are changed depending on any of R, G, and B as described above is as follows.

In general, in the case of a full-color sensor, since there is one of the color balances specific to the sensor, it is erroneous to make a chromatic / achromatic color determination with the same determination criterion for all colors. Therefore, as shown in FIG. 8, the color balance characteristics of the sensor are accommodated by dividing the three-dimensional RGB space into three parts. That is, the three-dimensional space of RGB is defined as MIN =
R is divided into an area 1702 where MIN = G, an area 1703 where MIN = G, and an area 1704 where MIN = B. Ka, kb, kc, ia, i
Use the values of b and ic.

For example, for a sensor in which the signal of the R component appears lower, by slightly increasing the values of KAR, KBR, KCR, iAR, iBR, and iCR in FIG. 4, when MIN = R, In the area shown in FIG.
It is possible to narrow the area, and it is possible to respond to various sensors finely.

 The subtractors 1310 to 1312 and the comparators 1316 to 1318 determine the magnitude relationship between MAX-ka, 2MINMAX-kb, MINMAX-kc, and 1 / 2MIN.

 The subtractors 1313 to 1315 and the comparators 1319 to 1321 determine the magnitude relationship between MAX-ia, 2MIN MAX-ib, MIN MAX-ic, and 1 / 2MIN.

 Comparators 1322 and 1323 determine the magnitude relationship between MAX, WMX MIN, and WMN, respectively.

From the above, the above area determination is performed, and the result is BL1, UNK
It is output as the judgment signal for 1, COL1.

[Outline of Processing Flow] FIG. 10 shows a processing flow of the apparatus in this embodiment.

First, after the power is turned on, if it is determined in 901 that the copy key has been pressed, the process proceeds to a copy operation and proceeds to 902.

In 902, a parameter for determining whether the original is black and white or color is set in the color determination unit 109.

At 903, a document determination scan is performed to determine whether the document is monochrome or color. In the document determination scan, only the reader unit operates and the printer unit does not operate.

As a result of the document determination, if the color is determined in 904, the full color copy operation from 905 is started, and if the color is determined to be black and white, the black and white copy operation is started in 910.

That is, during the color copy operation, parameters suitable for the copy operation are set in the color determination unit 109 in 905.

Further, a total of four main scans (scans for four-color printing) are performed from 906 to 909, and the signals subjected to the signal processing are output to the print 202, and the M, C, Y, and M signals are real-time in each scan. Bk toner is superimposed and full-color reproduction is performed.

On the other hand, in the black-and-white copying operation, in 910, the main scan is performed once, and black-and-white copying is performed only with the Bk toner.

[Original Judgment] Next, a method of original monochrome / color determination will be described.

As described above, the determination of whether a document is a white / black document or a color document is performed at the time of the document determination scan. In the document determination scan, the color determination unit 109 in FIG.
Thus, the chromatic pixel count means 117 counts the COL1 signal indicating that the pixel is a chromatic pixel, and determines whether the original is a color original or a white / black original.

FIG. 11 is a block diagram of the chromatic color pixel counting means 117.

1101 is an up counter, 1102 is a flip-flop, and the count value is cleared by the HSYNC signal. In the section where the COL1 signal is "1", the count value is counted up in synchronization with the CLK signal. The value N of a chromatic pixel included in one line is held by 1102.

On the other hand, reference numeral 1105 denotes a register which holds a value and Ref preset by the CPU 1106.

1103 is a digital comparator, which compares the magnitude of N and Ref, Output.

Reference numeral 1104 denotes an up counter similar to 1101, and 1107 denotes an inverter. When the count value is cleared when the VSYNC signal is “0” and the output of the comparator 1103 is “1”,
The count is incremented at the timing of the HSYNC signal.

As a result, by setting an appropriate value to Ref in advance, the number of lines having Ref pixels or more in one line is output from the counter 1104 and sent to the CPU 1106.

The CPU 1106 determines whether the original is a color original or a white / black original based on this value. That is, by sending the number of lines including chromatic pixels to the CPU,
For example, when this number is greater than a certain number of lines,
By determining that the document is a color document, it is possible to perform determination processing that is strong against noise.

It should be noted that, as in the above-described embodiment, this is performed in units of one line.
The number of chromatic color pixels may be counted for each line, several lines, or the entire original surface, and may be compared with a certain threshold value to perform an automatic color / monochrome determination.

[Main scan operation] Hereinafter, the main scan operation will be described.

[Mixing Circuit] The mixing circuit 112 is a circuit that appropriately weights the UCR / masked (Y, M, C, Bk) signal and the M signal that is an ND signal and outputs the signal. Here, the reason why the M signal is used as the ND signal is that the M signal is closest to the ND image among the Y, M, and C signals.

If the original is determined to be a monochrome original by the original determination scan, GAIN2 = 1 and GAIN1 = 0, that is, only M is output.

On the other hand, if the original is determined to be a color original,
GAIN1 and GAIN2 are switched according to each pixel.

FIG. 12 shows a character edge determination signal of a color determination signal in the “A” character read in various color states. FIGS. 12 (a) to 12 (c) show the determination signal for the cross section of the character a shown in FIG. 12 (d).

FIG. 12 (a) is a case where a black “A” character is read as black, and M2 indicating an achromatic density signal (hereinafter referred to as an ND signal).
The signal is read by blurring of the reading optical system as compared with FIG. 12 (d). The edge signal (EDGE) is formed in a shape bulging from the end of the character, and only the BL1 signal is generated as a color determination signal.

Here, since the M2 signal and the EDGE signal indicating the ND signal use a green color separation signal, FIGS. 12 (b) and (C) are also schematic except for the green characters, and FIG. Shows similar output. M2 signal and EDGE for green text
No signal is generated.

FIG. 12 (b) shows the case of reading the letter "A" composed of middle-saturation characters, in which a UNK1 signal indicating the middle-saturation is generated.

FIG. 12 (c) shows a case where the character “A” composed of black characters is read with a color shift, and the BU1 signal is thinner than in FIG. Saturation signal
UNK1 occurs.

FIG. 13 is an enlarged view of the section a in each case of the black character, the intermediate saturation character, and the middle saturation character of the black character in FIG. Here, V2 is a circuit 105 when the development colors are M, C, Y, and Bk.
3 shows an example of the output signal.

FIG. 13 (a) shows a case where black characters are read, and the circuit 105
, The color components of M, C and Y are reduced to about 20%. However, since this character is a black character, it is desirable to record using black toner as much as possible. Also, the twelfth
It is desirable to reduce the M, C, and Y color components as much as possible in the intermediate saturation generated at the edge of the black character as shown in FIG.

Therefore, in the present embodiment, as shown in FIG. 14, the UCR / Mask circuit 105 according to the result of the color judgment signal and the character edge judgment signal.
Color recording signal V2 (M ', C', Y ', K') and ND signal
Color recording is performed by appropriately mixing M2.

In FIG. 14 (a), it corresponds to the black character EDGE of FIG. 12 (a), and outputs a 0 signal (no development) when the development color is M, C, Y, and a density signal M2 when the development color is Bk. Is output. FIG. 14 (c) corresponds to the intermediate saturation edge of FIG. 12 (b). In this case, the developed color is changed to emphasize the black component of the edge.
For M, C, and Y, half of M ', C', and Y 'generated from 105 are output as color recording signals V2, and when the development color is Bk,
A signal obtained by adding 50% each of the K 'output of the color recording signal V2 and the density signal M2 is output.

FIG. 14 (f) corresponds to the non-edge portions of the black characters in FIG. 12 (a). Here, the M ', C', and Y 'components of the color recording signal V2 are reduced to 3/4 in order to improve the signal connection with the edge portion recorded in Bk single color, and the K' component of Bk recording is reduced. Three
One fourth of the density signal M2 is added to / 4.

The change of the image signal by the calculation of FIG. 14 will be described with reference to FIG. Here, V2 (M) means the output of V2 when PHASE = 0 (magenta development color). V2 (C), V2
(Y) and V2 (Bk) are V2 outputs for cyan, yellow and black, respectively.

FIG. 13 (a) is a black character portion, and the portion b is an edge portion corresponding to FIG. 14 (a). Here, M, C, Y
Is 0, and the density signal M2 is output as a Bk signal.

The portion C is a black non-edge portion corresponding to (f) in FIG. 14 and has V4 signals V4 (M), V4 (C), V4 of developed colors M, C, Y.
(Y) is 3/4 of V2 (M), V2 (C), V2 (Y), and Bk
Is a value obtained by adding 3/4 of V2 (Bk) and 1/4 of M2 as the signal of.

FIG. 13 (b) shows an intermediate chroma character, and the d portion is an edge portion corresponding to FIG. 14 (c). Here, V4 (M), V
4 (C), V4 (Y) is 1/2 of V2 (M), V2 (C), V2 (Y)
And V4 (Bk) is a value obtained by adding 1/2 of M2 which is 1/2 of V2 (Bk).

FIG. 13 (c) shows a case where intermediate saturation occurs in the edge portion of a black character. The edge portion e has the same processing as the d portion, and the non-edge portion has the same processing as the black portion (BL = 1) by the black determination. Is done. This reduces the color signal at the black character edge.

FIG. 14 (h) shows the case where EDGE = BL1 = 0, in which case U
V4 is equal to V2 regardless of the values of NK1 and COL1.

In this embodiment, multipliers 112-1 and 112-2 and an adder 112-3 are used in FIG. 1 to generate the V4 signal shown in FIG. Then, the multiplication coefficient generation unit having a width of the control signal generation unit 110 receives the color judgment signals BL1, UNK1, COL1, and CAN1 and the character edge judgment signal EDGE, and calculates the multiplication coefficients α = GAIN1 and β = CAiN2 of the multiplier. Occur.

The multiplication coefficient generator is constituted by a ROM as shown in FIG. 15 and receives a 5-bit determination signal and PHASE as an address, and outputs two gain signals GAIN1 and GAIN2 corresponding to three bits each. I do.

FIG. 16 shows the relationship between the ROM address and the output. The gain signal here is obtained by quadrupling the actual gain, and is multiplied by 1/4 in the multipliers 112-1 and 112-2. FIG. 17 shows details of the multipliers 112-1 and 112-2. The 8-bit image signal is quadrupled and doubled by bit shift type multipliers 2901 and 2902, respectively.
They are 3-bit gain signals GAIN (2), GAIN (1),
Selected by gates 2903, 2904, 2905 by GAIN (0) and added by adders 2906, 2907. After that, it is multiplied by 1/4 by the bit shift type divider 2908 and 255 by the 255 limiter 2909.
The above 9-bit data is all rounded to 255 8-bit data and output.

The color recording signal V2 and the density signal M2 weighted and added by the color determination signal and the character edge determination signal as described above are input to the spatial filter 117.

[Spatial Filter Unit] FIG. 18 shows a configuration diagram of the spatial filter 113 in the present embodiment. The spatial filter shown in FIG. 18 is an edge-enhanced filter using a Laplacian filter of 3 × 3 pixels, and the Laplacian multiplier can be switched between two types, 1/2 and 1.

3001 and 3002 are line delay memories, respectively. Image signal V for three lines generated by this line delay memory
4, V42 and V45 are delayed by one clock at flip-flops 3003 to 3006, respectively. Here, the target pixel is V43 and V4
1, V42, V44, V46 are multipliers 3007 to form Laplacian
It is multiplied by (-1) by 303010 and added by adders 3011, 3012 and 3013, respectively. Further, the target pixel V43 is quadrupled by the multiplier 3014 and the output of the adder 3015 is added by the adder 3015 to generate the Laplacian L. This Laplacian L is multiplied by で in a multiplier 3016. The pixel of interest V43 and L / 2 are added in the adder 3017 to generate a weak edge emphasis signal E1. The adder 3018 adds the target pixel V43 and the Laplacian L to generate a strong edge emphasis signal E2. These two types of edge-emphasized signals and the signal V43 of the pixel of interest itself are the control signal DFiL
(1) Selected by DFiL (0) and output as V5 signal. Selector when DFiL (1) is 0 and DFiL (0) is 1
At 3019, a weak edge emphasis signal E1 is selected and DFiL (1) is set to 1
In the case of, the strong edge emphasis signal E2 is selected and DFiN (0)
In the case of (3), the selector 3020 selects a signal SMG to which smoothing described later is applied and outputs it as a V5 signal.

The filter control signal generator generates a 2-bit DFiL signal consisting of the filter switching signals DFiL (1) and DFiL (0), and the filter control signal generator 110 is included in the control signal generator 110.

In the present embodiment, the black character edge portion is sharply emphasized so that the black character edge is sharpened. The edge enhancement is not applied to the non-character edge portion in order to prevent the color tone from being changed by the edge enhancement.

The character edge portion of the intermediate saturation and color is configured to apply a weak edge emphasis so that a change in color tone due to the edge emphasis is hardly noticeable while the edge portion is recorded in a sharp form. FIG. 19 shows a circuit of the filter control signal generator, and its logical formula is shown in FIG.

[Processing of Flat Area] The area not judged as EDGE by the character edge judgment unit 107 in the present embodiment includes a halftone original. When this halftone original is read in units of pixels using a CCD, moiré fringes occur due to the regularity of the pixels of the CCD and the regularity of the halftone original.

In order to prevent this, in this embodiment, the FILTER circuit 113 is configured to apply smoothing to a document area not determined as a character edge (an area having a high possibility of halftone dots). No.2 for smoothing filters
As shown in Fig. 21, the target pixel is multiplied by 1/2 and the surrounding four
For the pixels, a smoothing filter that multiplies by 1/8 and adds each is used.

FIG. 18 shows details of the FILTER circuit 113 in this embodiment.

In FIG. 18, adders 4201, 4202, and 4203 add four pixels V41, V42, V44, and V46 around the target pixel. An adder 4204 adds a signal V43F obtained by quadrupling the target pixel V43 to the signal.

The result is reduced to 1/8 by a bit shift type divider 4205 to obtain a smoothed filter signal SMG.

In the FiLTER circuit 113, the pixel of interest is delayed by one clock with respect to one line.
The signal is delayed by one line and one clock in the line memory 121 to become a DFiL signal. Similarly, the GAM signal from the gamma switching signal generator 110 and the SCR signal from the screen switching signal generator 111 are also delayed by one line and one clock to become DGAM and DSCR signals.

[Gamma Conversion Unit] The gamma conversion unit 114 performs image density conversion. The gamma conversion unit 114 is composed of Rom as shown in FIG. 22. The filtered 8-bit V5 signal is input as the address of Rom, and the corresponding gamma conversion output is the 8-bit V5 signal from the data terminal of Rom. Output as ViDEJ signal.

2 which is input to the address line together with the V5 signal
As shown in FIG. 23, four types of gamma conversion characteristics can be selected by the bit DGAM signal.

In FIG. 23, the case of DGAM = 0 is the case of input = output, which is applied to a non-character edge portion. DGAM =
In the case of 1, 0 to 255 as shown in the figure.
Inputs corresponding to the j-section on both sides generate outputs of 0 and 255, and slope between them. The conversion characteristic becomes useless with the straight line. This means that a video signal with a lower density is output for a nearby input that is a low-density input, and a
A video signal with a higher density is output, and an intermediate density of 128 is output.
Since the density change of the nearby input is emphasized, the character edge can be recorded more sharply. This DG
AM1 is adapted to color character edges.

If DGAM = 2, increase the value of j for DGAM = 1 to a larger
In addition, the character edge is recorded in the sharp. However, since the linearity of the input and output is lost, the color tone cannot be guaranteed. Therefore, DGAM = 2 applies only to mid-saturated character edges.

In the case of DGAM = 3, this is a characteristic using l of a value larger than K, and is applied to a black character edge for which sharpness is required.

The gamma switching signal DGAM is obtained by delaying the GAM signal from the gamma switching signal generator by one line and one clock by the line delay 121 as described above. Control signal generator 11
As shown in FIG. 24, the gamma switching signal generator in 0 is composed of Rom, and inputs a color determination signal and a character edge determination signal as addresses and outputs a GAM signal as data. Figure 25 shows the contents of the Rom table. As described above, the black character edge portion (EDGE = 1, BL1 = 1) has GAM = 3, and the intermediate chroma character edge portion (EDGE = 1, UNK = 1) has GAM = 3.
It becomes 2.

[PWM Modulator] The gamma-converted VIDEO signal is converted to a pulse width signal by the PWM modulator 115.

Then, by controlling the lighting time of the laser 213 with the pulse-width-modulated signal, a copy output 116 with gradation density expression is obtained.

 FIG. 26 shows details of the PWM modulation circuit.

The VIDEO signal is converted into an analog image signal AV by the D / A converter 3701. The image signal CLK synchronized with the VIDEO signal and the screen clock CLK4 having a frequency twice the frequency of the image signal CLK are toggle flip-flops 3702 and 3702.
At 703, the clock is synchronized with HSYNC and frequency-divided by 1/2, and converted into clocks CLK4F and CLKF each having a duty of 50%. These two clocks are transformed into triangular waves by the integrators 3704 and 3705, and then wave height adjusted by the amplifiers 3706 and 3707 to the output dynamic range of the A / D converter. Is compared to

Thus, the AV signal is converted into two pulse width modulation signals PW4 and PW. Thereafter, in the selector 3710, one of PW4 and PW is selected by the DSCR signal, and the laser drive signal L
It becomes DR.

FIG. 27 shows the operation timing of this circuit. As shown in the figure, a triangular wave TRi4 obtained by integrating a clock CLK4F obtained by dividing CLK4 by 1/2 is a triangular wave having a period of one pixel of an image. This triangle wave
Since the triangular wave changes in a substantially linear manner over the entire output range of the D / A converter, by comparing the triangular wave with the analog image signal AV, the AV signal is pulse-width modulated with one cycle of an image pixel section to become PW4. .

Similarly, since TRi is made of CLKF obtained by dividing the pixel clock CLK by 1/2, the AV signal is pulse-width-modulated by this TRi with one cycle of an image = pixel section to become PW.

PW4 signal pulse width modulated in one pixel cycle is clock C
Recorded by the printer at the same resolution as LK. However, when an image is recorded using the PW4 signal, the basic density unit is as small as one pixel, and therefore the gradation expression cannot be said to be sufficient due to the characteristics of the electrophotographic process used for the printer.

On the other hand, since the PW signal reproduces the density in units of two pixels, the gradation expression is sufficient, but the recording resolution is half that of PW4.

Therefore, in this embodiment, PW and PW4 are switched for each pixel by controlling DSCR according to the type of image. Specifically, PW4 is used for the black character edge portion and the intermediate saturation character edge portion that require resolution. PW is used for the color character edge portion and the non-edge portion in order to emphasize the color tone. However, it has been experimentally confirmed that it is better to use PW4, which emphasizes resolution, for color characters and edges, even if the color tone is sacrificed for documents composed of thin color characters such as maps. Accordingly, in the case of such an image such as a map, PW4 may be used.

The signal DSCR for switching between PW and PW4 is controlled by the control signal generator 1
The SCR signal from the screen switching signal generator in 10 is delayed by one line and one clock by the line delay 121. Details of the screen switching signal generator are shown in FIG.

As a result, in the DSCR in FIG. 27, the portion corresponding to the black toner development in the black or intermediate chroma character edge portion becomes Low, and PW4 is output as an LDR signal only in this section. At this time, even if the character edge portion is determined to be a character edge portion, in the case of a character edge portion having a color shift (CAN1 = 1), the PW4 signal is not used in order to prevent the deterioration of the quality of the recorded image due to the color shift being emphasized. It has become.

That is, a sharp character edge is required for a black character edge, and in the case of a color character edge, the reproduction of the color tone of the document is more important.

On the other hand, as shown in FIG. 13A, the M, C, and Y toners do not exist in the black character edge portion. Bk toner hardly exists in color characters due to the operation of the UCR circuit 105.
Further, in the middle-color saturation character edge portion, as shown in FIG. 13B, the Bk toner and the M, C, and Y toners are moderately present.

In consideration of the above characteristics, in the present embodiment, the pulse width modulation signal PW4 of one pixel period can be used for laser driving only in the character edge determination unit for the Bk toner.

As a result, a black character edge with a small number of color components can be originally realized, and a color character edge with a small amount of a color component is recorded only in the Bk component, and the color components retain the gradation, so color reproduction is maintained. Is also guaranteed.

[Document Determining Parameter and Main Scanning Parameter] In the document determining scan and the main scanning, the color determining unit 109 determines whether each pixel in the document is chromatic or achromatic. Will be The parameters for the determination at this time are different between the original determination scan and the main scan, and appropriate values for each are set in FIGS. 902 and 905.

Hereinafter, the appropriate values of the parameters in each scan will be described with reference to FIGS.

In FIG. 29 (a), reference numeral 1201 denotes a black-and-white original, and FIG. 29 (b) shows the R, G, B signal levels in the main scanning line including the edge portion C in the figure.

Ideally, it is desirable that all three signal levels of R, G, and B are equal. However, as shown in FIG.
At the edge portion of the point, a slight color shift occurs between max (R, G, B) and min (R, G, B).

Similarly, FIG. 30 (a) shows a color original, and the signal levels of R, G and B in the main scanning line including the edge point A and the red flat part B in the figure are shown in FIG. ).

As shown in FIG. 30 (b), at point A, max (R,
The difference between G, B) and min (R, G, B) tends to be slightly larger than point C described above.

Furthermore, at point B, max (R, G, B) and min (R, G, B)
And the difference is quite large.

The max (R, G, B) and min (R, G,
When the value of B) is plotted on the max-min plane shown in FIG. 7-1, it becomes as shown in FIG.

However, in the case of this scan, it is important to make a distinction between the point A and the point B, that is, the color character portion and the point C, that is, the black character portion, because the determination at each pixel is important.

Also, in the case of the original black-and-white / color determination scan, it is important to determine whether the entire original is color black and white, so that point B is reliably determined to be chromatic and point C is reliably determined to be achromatic. If it can be determined, point A may be determined to be achromatic.

In other words, the point C may be reliably determined as a black pixel in the present scan, and the point B may be reliably determined as a chromatic pixel in the pre-scan (document determination scan).

Considering this principle, the optimum criterion for determining the saturation for each scan is shown in FIG.

First, in the case of the present scan, that is, in the case of the black character determination scan, as shown in FIG. 32 (a), the points IA, B are determined as chromatic pixels, and the point C is determined as a black pixel. , ka, k
Determine the values of b and kc appropriately.

This is set with emphasis on the values of ka, kb, and kc for distinguishing the black area A in the saturation determination table of FIG.

On the other hand, in the case of the document determination scan, as shown in FIG. 33, if only point B can be reliably determined as a chromatic pixel, the number of chromatic pixels is counted by the counting means 117 to determine the black and white of the document. / Color can be determined, so that point A may be temporarily determined to be achromatic.
That is, FIG. 32 (b) is set with emphasis on ia, ib, ic in order to reliably determine the chromatic pixel area C in FIG. 7-1, and the values of ka, kb, kc are 0 ≦ ka ≦ ia 0 ≦ kb ≦ ib 0 ≦ kc ≦ ic Any value may be used. For example, assuming that ka = ia, kb = ib, and kc = ic, the intermediate pixel area (the seventh-
FIG. 1B) may be omitted, or the black pixel region may be eliminated by setting ka = kb = kc = 0.

As described above, at the time of the original determination scan, as shown in FIG. 32 (b), ia, ib, ic are set larger than those of FIG. 32 (a) (at the time of the main scan), and the points B and C are set. By using parameters that are clearly separated, erroneous determination can be reduced.

According to the above embodiment of the present invention, for the determination of whether a document is black and white or color, and for the detection of a black character portion in the document, under the different determination conditions for the same hardware, respective determinations suitable for each are performed. By realizing, processing with less erroneous determination can be performed. In addition, since hardware is shared in both processes, a high-performance device with an efficient configuration can be realized.

Although the above embodiment has been described using a digital color laser copying machine that performs printing using toner, the present invention is naturally applicable to a color image forming apparatus such as a color thermal transfer printer and a color ink jet printer. is there.

In the above embodiment, the color determination unit 109 and the chromatic color pixel counting unit 117 determine the black and white / color of the input image based on the input image signals R, G, and B.
A black character is determined based on R, G, and B. Then, the CPU 118 switches the parameters of the saturation determination criterion between the monochrome / color determination of the original (during pre-scan) and the black character determination (during main scan).

By changing the black pixel detection criterion between the pre-scan and the main scan, the parameters can be optimized so as to minimize erroneous determination in each determination.

Note that not only the parameters but also the black pixel determination algorithm itself may be switched between the pre-scan and the main scan.

[Second Embodiment] FIGS. 33 and 34 are views for explaining a second embodiment of the present invention.

FIG. 33 is a block diagram of the saturation judgment. In the figure, MAX and MIN are the same signals as those described in FIG. 1, and the adder 8001, the subtractor 8002, 8003, the squarer 8004, 8005, the multiplier
The determination signal J is generated via the 8006,8007 adder 8008.
J is calculated by the formula of J = (MAX + MIN-a) ² × b + (MAX−MIN) ² × c and is preset to 8003,8006,8007.
It is calculated according to the values of a, b, and c.

Here a, b, by selecting appropriate values of c, J ₁ <become curves curve and J = J ₂ as a J = J ₁ in J ₂ becomes appropriate constant elliptic curve as shown in FIG. 34 Indicated by Thus the value of J in the judgment circuit 8009 is compared with J ₁ and J _2,
The same determination as in FIG. 7-1 can be made.

According to the present embodiment, the use of the elliptic curve for the area division allows the area division to have more flexibility than the case of using a straight line.

The region can be divided by any other linear or non-linear equation, such as a hyperbola, a parabola, etc., without being limited to the elliptic curve of the present embodiment.

[Third embodiment] Fig. 35 is a view for explaining a third embodiment of the present invention.
FIG. 4 is a processing block diagram of a saturation determination.

9001 is an arithmetic unit that calculates (I, Q) in (Y, I, Q) space from (R, G, B). (I, Q) is calculated by the following equation. Since the hue can be determined by (I, Q), a switching signal of the selectors 1304-1309 can be output by programming the determination result in the ROM 9002 in advance.

Although (I, Q) is used in this embodiment, (L ^* , a ^* ,
b ^*) (a space, b ^*) and other chromaticity may be used a signal representative of the.

Further, the selector switching based on the hue is not limited to three, but may be six or twelve.

Further, as the selector signal, a MAX signal or a MAX signal and a MIN
Combinations of signals can also be used.

[Fourth Embodiment] Further, the scope of the present invention is not limited to a copying machine.
It is also effective in a file system as shown in FIG.

This system is configured by the same image skinners 4602 and 202 as the controllers 4601 and 201, the same color determination unit 4603 as the printers 4601 and 109 similar to the controllers, and the same image processing unit 4606 as the DISK memories 4605 and 211.

In this system, image data is communicated through any of the following paths: (1) image scanner → disk memory (2) image scanner → printer (3) disk memory → printer
In the pass of (2), the type of the document is determined by the document determination scan, thereby switching the output mode of the printer and writing the data in the DISK memory in black and white or full color. In addition, the throughput of monochrome printing can be improved (similar to the first embodiment), and the memory capacity of the DISK memory can be saved, and the memory can be used effectively for full color and monochrome image files. Can be used for

Further, in the passes of (2) and (3), as in the first embodiment, a clear output image without color misregistration is obtained by changing the processing for each pixel and outputting to the printer. Can be

As described above, according to the above embodiment, different suitable judgment conditions are used for the same hardware to determine whether a document is monochrome or color and to detect a black character portion in each pixel in the document. By judging by
The objective of the present invention is to improve the throughput and realize output processing with less color misregistration, to share hardware, and to limit the number of high-performance devices.

[Fifth Embodiment] An embodiment of the present invention described below allows the chromatic / achromatic judgment standard to be changed from the operation unit. It is possible to change to a preferable criterion according to individual differences, the purpose of use, preference of the operator, and the like.

[Description of operation unit]

FIG. 37 shows the appearance of the operation unit 1870 in this embodiment.

Numeral 601 denotes a numeric keypad for inputting the number of copies, etc., from 0 to 9;
It is for inputting numerical values up to.

A display panel 602 is a liquid crystal display panel which displays the current machine setting mode, paper size, copy magnification, etc., and informs the operator.

A reset key 603 is used to initialize a currently set mode. For example, it is used when a desired setting cannot be performed due to an erroneous operation.

604 is a clear / stop key, which stops the operation when the machine is in operation, and the number of sheets when the machine is not in operation.
Used to clear the numeric value set with the numeric keypad.

A copy start key 605 is used to start a copy operation.

606 selects a paper size, and the selected paper size (for example, A4) is displayed on the display panel 602.

Reference numeral 607 denotes a density key for adjusting the density of the copy from light to dark.
The current density level is indicated by the LED.

Reference numeral 609 denotes a document type mode selection key for selecting a character mode, a photo mode, or a character / photo mode depending on the type of the document.

Reference numeral 610 denotes an LED, which indicates that the character mode and the photo mode are selected, respectively.
Only one of the three is on.

611 is a control key, which includes an OK key 612, an up arrow (矢 印) key 613, a down arrow (▽) key 614, a right arrow () key 615, and a left arrow () key 616.
Used to move the cursor when setting each mode in 602.

An asterisk key 618 is used to determine a magnification according to the size of a sheet or to register a copy mode as described later.

An image create key 617 is used when processing and outputting an image or when adjusting various image processing conditions.

[Change of Saturation Judgment Criteria in Original Judgment Scan (Pre-Scan)] Even if the same original is determined as a black-and-white original or a color original, the same original may be determined due to variations in various characteristics of a reading system in the apparatus. . This is because the distribution of chromatic and achromatic colors on the max-min plane shown in FIG. 7-1 differs due to variations in various characteristics such as spectral sensitivity characteristics, resolution, and vibration conditions of the reading system. .

Further, depending on the purpose of use or preference of the operator, the determination as to whether the same original should be copied in a single black color or in full color may be different. For example, whether to copy a manuscript such as a newspaper with a yellowish background in plain black by skipping the yellow in the background or to copy it faithfully in full color including the background color depends on the purpose of use of the operator.

Thus, the above-described problem can be dealt with by changing the chromatic / achromatic determination criterion according to the purpose and preference of the operator using the operation unit 1870.

First, the method of changing the criterion for black / white / color determination (hereinafter referred to as ACS) of a document at the time of prescan will be described with reference to FIG.

This operation is adjusted and set in the manufacturing process of the product (the image processing apparatus using the present invention), or is notified to the general user on the premise that the service person requested by the user changes in the market. It can be changed by special key operation that is not performed.

In the state of the standard screen 1501, the key operation for changing the
37 Use the asterisk key 616 shown in
When the asterisk key 616 is pressed after pressing 9, 9, and 9, the state shifts to the change state 1502.

In the change state 1502, in the chromatic / achromatic judgment for each pixel, nine separation levels 1 to 9 are set depending on whether the achromatic judgment is given priority or the chromatic color is given priority in the achromatic / chromatic separation level. can do.

The method of dividing the separation level is not limited to the nine in the present embodiment, and may be finely or roughly divided. That is, when the separation level is 1, the achromatic color determination priority is the highest, and the area regarded as the achromatic color is the largest. When the separation level is 9, the chromatic color is the highest priority, and the area considered the achromatic color is the highest. Is minimized. In the case of separation levels = 2 to 8, levels 1 and 9 are appropriately allocated so that the area considered as achromatic is gradually narrowed.

In the change state 1502, the settings can be changed by operating the keys 615 and 616. For example,
With the separation level = 5 as in 1503, the separation level = 6 with the key, and the key separation level is increased by one so that the display of 1504 is obtained.

Conversely, the key changes the state of 1504 (separation level = 6).
The separation level is reduced one by one so that the state of 1503 (separation level = 5) is obtained.

The above procedure will be described with reference to the flowchart of the CPU 118 in FIG. 38 (b) and the block diagram in FIG. 38 (c).

First, at 4711, the user presses the asterisk key to make a predetermined setting and determines whether the user has entered the separation level setting mode. If you enter the setting mode,
Fig. 38 (c) shows the screen for adjusting the ACS chromatic / achromatic separation level.
Is displayed on the display panel 602.

Next, at 4713, the ACS tangible / intangible separation level is changed using the control key 611. When a change is input, the color determination unit 109 of FIG. 38 (c) changes the saturation determination criterion in 4714 as described later.

Then, when the level setting is completed, the OK key 612 is depressed, and the flow ends.

FIG. 39 shows a specific example of changing the determination conditions for the chromatic / achromatic separation levels 1 to 9.

That is, iAR,
By setting the values of iAG..., iCB, WMN, and WMX in the color determination unit 109 by the CPU 118 for each of the separation levels 1 to 9 in FIG. Can be.

Here, the separation level data shown in FIG. 39 is stored in the RAM / ROM 120 (FIG. 38).
(C) of FIG. Separation level data is stored in the ROM for levels 1 to 9 and the address 1
By giving 〜9, values of iAR 発 生 WMX may be respectively generated.

[Change of Saturation Judgment Criteria in This Scan] The above is the description of the document judgment scan (ACS).
Although the criterion for determining whether the original is black, which is a color, is changed, the same chromatic / achromatic separation level adjustment is also possible in the processing in this scan. That is, in the first embodiment, the function of copying a black character portion in a single black color is provided, but the criterion for this determination can be changed.

The procedure for setting the chromatic / achromatic separation level in this scan is almost the same as that in the case of ACS described above. FIG. 40 shows a change in the screen on the display panel as an alternative to FIG. 38 (a). Also in this scan, as shown in FIG. 41, the corresponding KAR, KAG,.
B in the flowchart 905 of FIG.
May be set as the criterion. This separation level is set independently of the separation level in Fig. 40, and is displayed on the standard screen 4701 as shown in Fig. 40. , 9,9,8, By pressing the key and using keys / keys, levels 1 to 9 can be selected. Here, the parameter of the separation level in the present scan may be the same as the parameter of the separation level in the pre-scan (ACS).

By adjusting the separation levels 1 to 9, it is possible to adjust the individual difference of the apparatus and to finely correspond to the usage purpose of the operator to the preference.

As described above, according to the above-described embodiment, when performing chromatic / achromatic determination on a color image signal obtained by reading a document, the determination level can be changed from the operation unit. It is possible to adjust variations in various characteristics between individual devices, and to finely respond to the purpose of use, preferences, etc. of the operator.

In addition, as described above, in addition to changing the parameters of black pixel determination by the main scan and the prescan, the black pixels are determined by the prescan, and the result is stored in one image or several lines, for example, in a hit map memory. In this scan, black pixel processing may not be performed.

The change of the parameters for black pixel determination in the main scan and the pre-scan may be performed by the CPU as described above, and the saturation determination data may be stored in different table ROMs, and the parameters may be changed in the main scan and the pre-scan. May be selected.

〔The invention's effect〕

As described above, according to the first aspect of the present invention, it is possible to perform a highly accurate determination by switching the determination conditions in the black / white / color determination and the black character determination.

According to the third aspect, it is determined whether the original is monochrome or color at the time of preliminary scanning, and if the original is color based on the determination result, black character processing is performed when copying the original at the time of main scanning. By using the black-and-white color determination result obtained by the preliminary scanning, it is possible to efficiently realize high reproduction of black characters when copying a color original.

According to the sixth aspect, when the original is a color original, it is possible to perform a dedicated process on black characters whose reproducibility is deteriorated due to a color shift or the like, and the reproducibility of the black character portion identified according to the edge information of the color image is made possible. Improvement can be realized.

[Brief description of the drawings]

1 is an overall circuit diagram of a first embodiment of the present invention, FIG. 2 is an overall view of an image processing apparatus, FIG. 3 is a block diagram of an image scanner, and FIG. 4 is a block diagram of a color determination unit. 5-1 and 5-2 are diagrams showing a MAX-MIN detection circuit and a truth value. FIGS. 6-1 and 6-2 are circuit diagrams of a selector and a diagram showing truth values. FIGS. 1 and 7-2 are diagrams showing judgment criteria and judgment signals, FIG. 8 is a diagram showing R, G, B spaces, FIG. 9 is a timing chart, and FIG. 11 is a chromatic pixel count circuit, FIGS. 12 and 13 are diagrams showing signal levels of character portions, FIG. 14 is a diagram showing mixing conditions, and FIGS. 15 and 16 are mixing diagrams. FIG. 17 is a circuit diagram of a multiplier, FIG. 18 is a circuit diagram of a filter, FIGS. 19 and 20 are diagrams illustrating filter switching conditions, and FIG. 21 is a smoothie. FIGS. 22 to 25 are diagrams for explaining switching of gamma conversion, FIGS. 26 to 28 are diagrams for explaining switching of laser drive signals, and FIGS. 29 and 30 are character portions. 31 and 32 are diagrams showing judgment conditions, FIGS. 33 and 34 are explanatory diagrams of a second embodiment of the present invention, and FIG. 35 is a third embodiment of the present invention. FIG. 36 is an explanatory view of a fourth embodiment of the present invention, FIG. 37 is an external view of an operation unit of a fifth embodiment of the present invention, and FIG. FIG. 39 illustrates an achromatic separation level setting, FIG. 39 illustrates a specific example of an ACS chromatic / achromatic separation level, and FIG. 40 illustrates a display panel when the chromatic / achromatic separation level for black character determination is set. FIG. 41 is a diagram showing a specific example of a chromatic / achromatic separation level for black character determination. 108: character edge extraction unit 109: color determination unit 117: chromatic pixel counting unit 118: CPU 112: mixing circuit 113: spatial filter 114: gamma correction unit 110: control signal generation unit

Claims (5)

(57) [Claims] 1. A means for determining black and white / color of an input image based on an input image signal, a means for determining black characters based on the input image signal, and a means for switching a determination condition between the monochrome / color determination and the black character determination An image processing apparatus characterized by the above-mentioned. 2. The black-and-white / color judgment and the black character judgment use the same saturation judgment method, and the black-and-white / color judgment uses a judgment condition such that a chromatic color is judged more reliably than a black character judgment. The image processing apparatus according to claim 1, wherein: 3. A preparatory scan of the original is performed to determine whether the original is monochrome or color. If the result of the determination is that the original is color, black character processing is performed when copying the original during main scanning. Performing an image processing method. 4. The apparatus according to claim 3, wherein at least the saturation determination is common between the document determination for determining whether the document image is black and white or color and the black character portion determination in the black character processing. The image processing method described in the above. 5. An input unit for inputting image data corresponding to a document, a determination unit for determining whether the document is a color document or a monochrome document based on the image data input by the input unit, Identification means for identifying a black character portion of the original for each pixel from the edge information of the image data obtained, and processing means for performing black character processing on the identified black character portion when the color original is determined by the determination means. An image processing apparatus characterized by the above-mentioned.